Electronic fluid flow control valve



Jan. 14, 1964 w. L. HARRlEs ELECTRONIC FLUID ELow CONTROL vALvE Filed June 10, 1960 1N VEN TOR wr/vfoaa L. #A 'QR/E5 BY Paw (X1-CN A Z' TORNEY United States Patent O 3,117,416 ELECTRNIC FLUiD-FLOW CDNTROL VALVE Wynford L. Harries, Upper Montclair, NJ., assignor to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Filed `lune 10, 1950, Ser. No. 35,247 14 Claims. (Cl. dll- 355) This invention relates, in general, to liuid flow control systems, and, particularly to apparatus for electrically controlling the flow of fluids which supply ions in ion accelerating systems such as ion motor and the like.

In connection with ion motors and other ion accelerating devices, the fuel, or particles which are to be ionized and accelerated, must be delivered to the accelerating region in a beam of precisely controlled density in order to precisely determine the reactive thrust of the motor. Further, it is necessary lto provide rapid control over the supply of accelerated ions in order to properly control the motor in some of its uses. To accomplish this control it is necessary to control either the electric field which accelerates the ions or the passage of ionizable fiuid into the region containing the accelerating field. The former is unwieldy because of obvious arcing problems associated with the rapid variation of a high accelerating potential and sputtering, or erosion problems associated with collisions between misdirected, highly accelerated ions and the controlling electrodes, following rapid control variations. On the other hand, control of the passage of the ionizable fluid has been limited because of the clumsy and unreliable mechanical valves hitherto required for such control.

Accordingly, it is an object of this invention to provide improved apparatus for electrically controlling the flow of fluids.

Another object is to provide improved apparatus for controlling the density of ions in an accelerated beam of ions, especially in connection with an ion motor.

Still another object is to provide apparatus for controlling the thrust of an ion motor, particularly by the use of apparatus readily adapted to be controlled from a remote location.

In accordance with these objects, a general feature of the invention concerns the provision of a fluid flow control system including a liuid having a given associated flow path, and means for establishing a controlling electrical field along this path. In the region occupied by the control field the huid acquires ions either by collision ionization of the uid particles, or the ions are supplied by a suitable source of ions. Means are further provided for varying the polarity and magnitude of the control field so as to cause the ions to react with the liuid and variably aid or oppose the ow of the fiuid through the control region, depending upon the instantaneous polarity of the control field.

In accordance with a more specific aspect of the invention as applied to an ion motor, uid from a source of ionizable fluid passes through a flow path including first and second relatively exclusive regions. First and second permeable conductive members situated respectively in the first and second regions, intercept all of the fluid traversing the respective regions. The material and environment of` the conductive members is such that the intercepted fluid is ionized upon contact with the surfaces of the members. A potential applied between an accelerating electrode in the second region and the second conductive member serves to accelerate the ionized fluid and expel it at high velocities from the second region. On the other hand, a selectively variable potential applied between the first and second permeable members serves to control the ow of ions between the members while ice producing relatively little if any, acceleration of the ions, compared to that produced in the second region, thus varying the pressure differential between the un-ionized fluid entering the first member and the ions in the uid issuing therefrom. The first member thus constitutes an electronic valve which rapidly and sensitively controls the rate at which the fluid to be ionized is delivered to the second, or ion accelerating, region, and thereby controls the combined reactive thrust of the expelled ions.

These and other objects and features of the invention may be m0re fully appreciated upon consideration of the following drawings and specification wherein:

FIG. l is a drawing in cross section of a preferred embodiment of the invention as applied to an ion propulsion rocket including fuel flow control apparatus arranged in accordance with the teachings of this invention;

FIG. 2 is a cross sectional View of modified control apparatus for use in conjunction with the rocket system of FIG. l; and

FIG. 3 is a cross sectional view of still another variation of the ow control apparatus of thisinvention.

Referring to FIG, 1, a preferred embodiment of the invention, as applied to an electronic fuel control system in an ion propulsion rocket motor, includes a huid source 1. The fluid issuing from this source is an ionizable fluid, preferably vaporized cesium in this instance. This fluid is passed through an electrically actuated coarse con- -trol valve 3, into a chamber 4, bounded by a porous tungsten element 5, situated transverse to the walls of the chamber, and intercepting all of the fluid flowing out of the chamber. The chamber and porous tungsten element 5, are heated by means of heating coils 21, to a temperature at which the cesium is vaporized and further at which molecules of the vapor, diffusing through the pores of the tungsten element, are positively ionized by collisions with the walls of the pores, such ionization being attributable to the well known resonance ionization phenomenon relating to the ionization of metallic vapors, such as cesium, rubidium and potassium at temperatures above a given temperature, where the vapor is maintained in Contact with the surface of a conductive material having a work function greater than the ionization potential of the vapor.

The pores of the tungsten elements are of very small dimensions, on the order of one micron in mean diameter, in order to insure complete ionization by collision of the cesium vapor as it diffuses through the element 5. Sheets of porous tungsten approximately O.l inch thick and having the required pore diameter are now commercially available. The outer surface 30 of element 5 is partitioned into generally convex segments so as to concentrate the positive ions in regions 31 where they are maximally influenced by electric field forces maintained between the element 5 and accelerating electrodes 11. Electrodes 11 are maintained at a relatively high negative potential, -V, with respect to the element 5 by means of a high Voltage supply 13, which is referenced to a ground potential, as indicated at 14. Element 5 is also coupled to ground through conductor 17 having reference terminals 19 and 25 connected thereto. The electric field between electrodes 11, and element 5, accelerates the positive cesium ions issuing from the element, thereby forming directed streams 7, of accelerated positive ions. This stream passes through the space between the electrodes 11, to the exterior of the rocket engine, propelling the engine by thrust impulse reactions. Electron emitters 15, situated to the rear (right) of electrodes 11, introduce electrons into the accelerated positive ion stream, thereby electrostatically neutralizing the expelled stream with respect to the rocket engine, and thus with respect to the vehicle propelled therewith.

The foregoing rocket engine is somewhat more fully illustrated and described in an article in the October 1959 issue of Astronautics, vol. 4, No. l0, on page 34, by A. T. Forrester and R. C. Speiser, entitled Cesium Ion Propulsion. This article discusses the theory and operation of the cesium ion motor, withcontrol of the feeding of the cesium accomplished therein by means of a physically variable valve opening which is electrically actuated, as in the illustrated coarse valve arrangement 3, of FIG. l. The difhculties and disadvantages involved in the use of such physical mechanisms to control ion propulsion rockets, and, to a great extent, the use to control any fluid flow, may be enumerated as follows:

The physical valve requires power for manipulation;

It is diihcult to adjust the physical valve so that it offers stable impedance to the fluid while responding sensitively to signals commanding given variations in such impedance;

It is dicult and costly to adapt the physical valve for control from a remote location;

The moving parts of the physical valve decrease the speed of operation, reliability, and efficiency of the fluid flow control system; and

The physical valve is heavy (in relation to the arrangement of this invention).

In contrast to the foregoing, the present invention involves none of the above mentioned dieulties. Referring again to FIG. l, the preferred control arrangement of this invention is an electronic control valve comprising a permeable conductive member 6, which further partitions chamber 4 into two regions, 9 and l0, and intercepts all of the fluid flowing between the two regions. In the illustration of FIG. 1, member 6 is taken to be a porous tungsten element similar in cross-sectional structure to the ionizing member S, although, as will be explained hereinafter, the function of member 6 is quite different from that of member 5, and accordingly the composition and shape of the two members may differ radically.

Coupled between the members S and 6, is an electrical circuit including terminals 19 and 18 coupled respectively to the members and 6. Terminal 19 is coupled to the ground reference as at 25, while terminal 18 is coupled through a switch 20 and a potentiometer 24 to ground, thus completing the circuit. Potentiometer 24 includcs a stationary resistor 23, Center-tapped to ground. The potentiometer further includes a wiper arm 27, which serves to vary the resistance interposed between the switch 20 and ground, as shown. Across the ends of the resistor 23 a source of voltage. such as a battery 2S, in series with a switch 26. is utilized to selectively vary the potential difference between the ends of the resistor, and thus selectively vary the potential between wiper arm 27 and ground. Accordingly, when switch 20 is closed, and switch 26 is maintained open, a variable external electrical resistance, determined by the position of wiper arm 27, of potentiometer 24, is coupled between the permeable conductive members S and 6. Cesium vapor passing from the region 9 through the member 6, is resonantly ionized by Contact with the interior surfaces of the pores of the member, and thus the cesium is positively ionized as it enters the region of the chamber 4. In acquiring its positive charge, the ionized vapor gives up electrons to the member 6, tending to electrostatically charge the member 6 negative with respect to the member 5. Thus, with switch closed, and switch 26 open, a difference in potential tends to develop between the members 5 and 6 and this difference is of a polarity such that it tends to attract the positive ions in space 10 towards the member 6, inhibiting the flow of cesium therethrough and thereby exert a reverse pressure on the cesium vapor in the pores of the member 6. With switch 20 in the open position, and switch 26 still in the open position, the external resistance between the members 5 and 6 is, in effect, infinite, and a maximum electrostatic po- CFI tential difference is developed between members 5 and 6 which maximally inhibits the ow of fluid through member 6.

With both switch 26 and switch 2f) closed, battery 2S introduces an external potential difference across the members 5 and 6, at a polarity and magnitude determined by the position of wiper arm 27. This external potential difference may now be used to either enhance the flow of uid between the regions 9 and 10, or inhibit such flow in the manner previously described in connection with the internal potential difference developed by the flow of ions between the conductive members. The use of the external voltage source 2S, is advisable where a wide range of sensitive control is required.

The elements 5 and 6 in the illustration of FIG. l are both approximately l/o of an inch in means width. It should readily be appreciated that the combined widths of the two elements, in this instance 1/3 inch, determines the time lag between the actual turning on of the electric valve 6 following a maximal reversal of potential across the members 5 and 6, and the desired time at which such turning on should have occurred. This is due to Well known physical considerations involved in the initiation of fluid ow across a boundary following removal of an obstruction to such ow.

It should now be noted that the invention differs from conventional electronic control arrangements in that the controlling electrode, in this instance the member 6, is not interposed between the point of origin, at the member 5, of the ions which are to be accelerated and the accelerating electrodes. Instead, the control member 6 is positioned behind the source of ions, and controls the delivery of ionizable vapors to the ion source. Between the members 5 and 6, the fluid ow is mainly by diffusion, although there is some slight acceleration of ionized particles, as a result of the potential difference between the members. However, this acceleration is, as indicated, very slight, relative to that produced by the accelerating electrodes, and there is thus no resultant effect upon the acceleration of the ions produced by the member 5, at the surfaces 30. Hence, another advantage of the present invention is that the control arrangement in no way interferes with the field configuration in the region between the accelerating electrodes and the member 5. The

member 5, thus serves as an electrical shield between the accelerating electrodes 11, and the control electrode 6.

Those ions which are formed by collision between the cesium vapor and the pores of the member 6, upon reaching the member 5, become associated with ground electrons, and drift through the member 5 as a relativeiy neutral charge pair, the ions emerging at the surfaces 30. again exhibiting positive charge. Accordingly, it is seen that no acceleration is experienced by the ions, as they drift through the member 5, in response to the electric field between the electrodes 11 and the member 5.

It is now clear that the member 5 completely shields the control member 6 from the accelerating electrodes 1l and also shields the field of the accelerating electrodes from the control field associated with the member 6. This relative freedom from interference between the control and accelerating electrical fields is highly advantageous, since any such interference would tend to cause dispersion or deviation of the ion streams 7. and thus direct the highly accelerated ions at the accelerating electrodes 11, and the walls 34, of the ion propulsion engine. As a result, ions will collide with the surfaces of electrodes 11 and the inner surfaces of the walls 34, causing these surfaces to become eroded, or as it is more specifically characterized in the electronic arts, sputtered.

It should readily be appreciated that, with switch 26 closed, the ion motor of FIGURE 1 may be remotely' controlled by substituting for battery 28, a detector of remotely transmitted energy.

Referring to FIG. 2, a modification of the control arrangement of FIG. 1 includes the porous tungsten member 5 which supplies ions for the accelerating electrodes of the rocket. engine by means of resonance ionization with cesium vapors. The control system further includes a member 6 which partitions the chamber 4 into two regions 9 and 10, the region 1li being further subdivided into regions 16 and 10"'by a reference electrode 5 which is disposed between the members 5 and 6'. h'len'iber 6' is again a porous tungsten control member electrically connected to an external circuit 35 as in FIG. l, through terminal 18. The other terminus 19 of the circuit 35 is connected to the conductive grid 5. Here again, the iiow ot' cesium from the region 9 into the region 10 is controlled by the difference in potential across the terminals 18 and 19. When this difference is such that terminal 18 is suiiiciently negative with respect to terminal 19 all ion ilow ceases, and the pores of the member 6 become clogged with space charge ions which exert a back pressure inhibiting the further flow of cesium vapor in the direction of member 5. Conversely, when terminal 1S is sufficiently positive with respect to terminal 19, positive ions are accelerated towards the electrode S from member 6. At the electrode 5', the accelerated ions tend to 'oecome neutralized, and thereafter drift, by thermal agitation, or otherwise, into the region 10, and then through the member 5, emerging in the ion stream 7 ilustrated in FIG. l.

In summation, the apparatus described in connection with FIGURES l and 2, includes first and second porous conductive members designated 6 and 5 respectively, which respectively define first and second electrically isolated regions along the flow path of an ionizablc vapor, and also ionize the intercepted vapor. The irst region may be viewed as a control region (region 1G) wherein the ionized vapor, although not appreciably accelerated, is subjected to controlling electrical forces which vary the pressure of the ionized vapor in the `first region, in relation to that of the un-ionized vapor entering the region through the iirst member, thereby varying the rate of ilow of the vapor. The second region may be viewed as an accelerating region wherein the ionized vapors issuing from the second conductive member are focussed into ion beams which are accelerated and expe-i ed at high velocities from the second region, by means of an accelerating electric field maintained betweei the seconl conductive member and an accelerating ele trodc provided for that purpose.

Referring to FiG. 3, still another modification of the control system of this invention includes a porous conductive member 6" through which flows a iluid wr to be flow controlled. In this modification, me .tu not necessarily ionizable. A source of ions 4G, is positioned so as to introduce ions into tac iiuid issuing from member 6". The polential between terminals lS andv 19 then serves to establish ion currents which more or less oppose the motion of the huid through the menthe 6". Thus, in this instance, it may be appreciatey that porous member 6 need not be fabricated of tungsten, and further, it may be appreciated that this member may' otherwise differ radically' from the porous member t5 of FlG. l, in that the size of the pores is less c 'tical in member 6". It will be recalled that the porc size of member 6 of FIG. 1 is critical since member 6 must ionize the fiuid as it passes through the member. However, in the arrangement of FIG. 3, it is not necessary to ionize the iiud, nor is it required that the fluid be ionizable, this arrangement serving merely to regulate the iluid flow and not necessarily to regulate the flow of ionized fluid into an ion accelerating system.

Considering once again the control of an ion propelled vehicle by means of the ion rocket control system ot' FIG. 1, it should readily be appreciated that it is not only necessary to control the magnitude of the thrust exerted by ions expelled from the ion motors of the vchicle, but it is also neccssar to control the attitude ofthe vehicle. The latter control is obviously necessary for steering the venicle to the required destination, and it is also necessary for the less obvious purpose of overcoming undesired pitch, roll, and yaW disturbing forces which are exerted on the vehicle by the expelled plasmar trailing behind the vehicle. The word plasma as used herein refers to an expelled fluid mass which is electrically nr tral with respect to the expelling body. Hence the quotation marks above are used to indicate that the plasma, trailing behind the ion propelled vehicle considered herein, is not truly neutral, but includes a variable distribution of charge which exerts disturbing forces on the expelling vehicle. That this is so is evidenced by statements in an article in the November 1959 issue of Astronautics, vol. 41, No. 11, on page 37, by E. Stuhlinger and R. N. Seitz, entitled Ion Propulsion. This article clearly indicates the need for a highly sensitive and rapidly responsive thrust and vehicular attitude control system, for use with ion propulsion rockets. This need can truly be by utilizing a plurality of ion engines and associated control arrangements in accordance with the apparatus of FIG. 1 to rapidly and sensitively vary both. the propulsive thrust on, and the spatial orientation of the vehicle upon which the engines are mounted. The foregoing thus comprises a steering arrangement requiring no movingr parts for operation.

Although the invention has been described with reference to particular aspects thereof, it is to be clearly understood that many modifications are permissible without departing from the scope and spirit of the invention.

I claim:

1. An electronic fluid ow control system a source of lluid, means restricting said lui a given low path, means for establishing a uniform distribution of ions throughout a section of said flow path, means for setting up an electric field along said ow path, and means for controlling the ow of said fluid by varying the direction and magnitude of said electric li-:ld along said flow path.

2. An electronic fluid iiow control system comprising a source of fluid, means restricting said Huid to flow al ng a given flow path, a rst conductive member mounIcd so as to permeably intercept all of said liuid traversing said given path, means for cstabiishing a uniform distribution of ions throughout a section of said path cnclosiz 2 said first memb r, a second conductive member moi at a distance along said path from sat' st member. sa l first member being situated intermediaire said second member and said source of fluid in relation to 'l c, b.

means for applying an e iirst and second conductive members a trolling the flow of said iiuu and polarity of said applied potential pressure of said ions in relation to said iiuid.

3. An electronic fluid flow control 3 :zu confpiinn a source of fluid, means restricting said ilu. to iiow along a given flow path, means partitioning sc. l path inlo Y and second regions along said flow pm. id first r: being situated intermedi te said sour e and region, said partitioning means inclu-.lim n". trically isolating said lirst and second reg' id .system further including means ior establishing a ui form distribution of ions across said lirst region, means for setting up a first electric cld along said path in said to control the ow of said liuid by controlling s id ions in said iirst region, and means for setting up a second cie:- tric field in said second region to accelerate ions ente-ri g said second region.

4. An ion accelerating system comprising a source of ionizable iluid, rst means restricting said fluid to dow along a given path, second conductive means lining iii and second regions along said iiow path, said trst region being situated intermediate said source and said second region, said second conductive means having a work function sufficient to ionize said lluid, means disposed within said first region for permeably intercepting all of said fluid issuing from said source, said disposed means having a work function suflicient to ionize said liuid by collision contact, means for setting up an electric field in said first region for controlling said fluid by controlling the movement of ions within said first region relative to said disposed means, and means for setting up an electric field in said second region for accelerating ions entering said second region.

5. An ion accelerating system comprising a source of ionizable fluid, means defining a given flow path for said fluid, said path including rst and second mutually exclusive regions, said first region being situated intermediate said source and said second region in relation to said path, a first porous conductive member permeably intercepting all of said fluid in said first region, a second porous conductive member permeably intercepting all of said fluid in said second region, said first and second porous members having work functions greater than the ionization potential of said fluid, means for heating said first and second porous members to ionize said intercepted fluid in said first and second regions, respectively, at least one accelerating electrode mounted in said second region, means for maintaining said second member at a reference electric potential, means for applying a control potential with respect to said reference potential to said first porous conductive member, means for varying said control potential, and means for applyingr an accelerating potential with respect to said reference potential to said accelerating electrode.

6. An ion accelerating system according to claim 5 wherein said fluid is an alkali metal vapor taken from the group consisting of cesium, rubidium, and potassium.

7. An ion accelerating system according to claim 5 wherein said first porous conductive member is comprised of a sheet of porous tungsten.

8. Ari ion accelerating system according to claim 7 wherein said pores of said first member are approximately one micron or less in mean diameter to ensure maximal ionization of said fluid in said first region.

9. An ion acceierating system according to claim 7 wherein the separation of said first and second porous members and t'ne range of variation of said control potential are limited to provide negligible acceleration of said ions in said first region relative to the acceleration of said ions in said second region thereby preventing sputtering within said first region.

10. An ion accelerating system according to claim 9 and further including a control reference electrode mounted in proximity to said first member in said lirst region between said first and second members, and means for maintaining said reference electrode at said reference potential thereby increasing the sensitivity of control of said system in said first region, while further decreasing the acceleration of said ions in said first region.

ll. An ion motor comprising a source of alkali metal Y vapors taken from the group consisting of cesium, rubidium and potassium; means defining a given flow path for said vapor, first and second permeable conductive members which respectively define first and second regions along said path and permeably intercept all of said vapor traversing said regions, said first and second members including vapor intercepting surfaces having work functions greater than the ionization potential of said vapor,

means for heating said first and second members to ionize said intercepted vapors, an accelerating electrode mounted in said second region, means for applying a control potential between said first and second members, and means for applying an accelerating potential between said accelerating electrode and said second member.

l2. An electronic fluid flow control system comprising a source of a flowing fluid, a member enclosing the fluid issuing from said source, said member including at least one electrically conductive region which is permeable to said enclosed fluid, means for establishing a uniform distribution of ions throughout said fluid issuing from said permeable region of said member, means for setting up an electric field uniformly distributed over all of said permeable region of said member and extending everywhere along the direction of movement of said fluid issuing from said region, and means for varying said electric field to vary the back pressure exerted by said ions on said member and thereby to control the flow of said fluid.

13. An electronic fluid flow control system comprising a source of an ionizable flowing fluid, a member enclosing said source, said member including at least one electrically conductive region which is permeable to said fluid and which is comprised of a material capable of ionizing said lluid by collision as it traverses said region, means for setting up an electric field terminating in and covering said region of said member and extending everywhere from said region in the direction of movement of said uid emerging from said region, and means for varying said electric field to vary the back pressure of said ions in said emerging fluid against said region, and thereby to control the movement of said fluid through said region.

14. A controllable ion source comprising in combination a source of ionizable flowing fluid, a first member enclosing said source including a first conductive region which is permeable to said flowing fluid and which is comprised of a material capable of ionizing said fluid by collision as it traverses said region, a second member enclosing said fiuid traversing said first region, said second member including a second conductive region which is permeable to said fluid and which is comprised of a material capable of ionizing said fluid by collision as it traverses said second region, a third conductive member situated in the path of flow of said fluid traversing said second region at a distance from said second member which is large in relation to the maximum separation bctween said first and second members, means for impressing a first potential difference between said first and second conductive regions of said respective first and second members, means for controlling the rate of flow of said fluid by varying said first potential difference ovcr a predetermined range to produce corresponding variations in the back pressure of said ions on said fluid issuing from said first region, and means for applying a second potential difference between said second region and said third member for accelerating ions issuing from said second region.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN ELECTRONIC FLUID FLOW CONTROL SYSTEM COMPRISING A SOURCE OF FLUID, MEANS RESTRICTING SAID FLUID TO FLOW ALONG A GIVEN FLOW PATH, MEANS FOR ESTABLISHING A UNIFORM DISTRIBUTION OF IONS THROUGHOUT A SECTION OF SAID FLOW PATH, MEANS FOR SETTING UP AN ELECTRIC FIELD ALONG SAID FLOW PATH, AND MEANS FOR CONTROLLING THE FLOW OF SAID FLUID BY VARY- 